Scaling isn't that difficult if you take a reference point (e.g. one corner of the bitmap) and multiply or divide the relative distances from any point in the bitmap by your scaling factor. However, the results are generally quite lousy, especially if you don't use a whole numbers as scaling factors (which will run you out of LCD space quickly).

Rotating a bitmap is done is a similar way, but then you need to calculate the relative movement of all points in both the X and Y directions (using sin and cos functions). Again, the results are generally lousy as well.

There are quite some sites on the internet where scaling and rotation of images is discussed in great depth. Google around a bit and become a bsc in it, I would say.